A Study On The Influential Factors Of Water Requirement Of Crops In Hexi Region And The Optimal Distribution Of Water Resources

Agricultural water consumption accounts for more than 80%in the Hexi region,which is mainly composed of irrigated agriculture.Agricultural development is the most violent human activity to oasis ecosystem.There is a problem of low water efficiency and serious waste of water resources.So,the contradiction between water supply and water demand is very prominent.Climate fluctuation,planting scale change,crop structure adjustment and engineering water saving measures can all affect the demand of agricultural water resources from different levels.It is the result of multi-factor.Based on the water footprint,this paper analyzes the crop evapotranspiration(ETc),water deprivation,green water footprint,blue water footprint and gray water footprint of spring wheat,maize and potato,cotton,flax,rape,vegetables,melons,apples and grapes in the basin scale including Shiyang River Basin,Heihe River Basin and Shule River Basin from 1991 to 2013 by introducing the water stress index(WSI)and water deprivation.Further more,we mainly studied the driving mechanism of climate factors including precipitation,wind speed,relative humidity,minimum temperature,maximum temperature,average temperature,sunshine hours and socioeconomic factors including agricultural economy development,population size,planting structure adjustment,water intensity and industrial structure adjustment to crop water requirement.With the purpose of rational allocation for regional water resources,a multi-objective optimization model was established under the premise of virtual water subdivision and virtual water trade.Based on the research of this paper,the following conclusions are drawn:1.In terms of response to climate change of crop water deprivation.(1)The economic and technical water deprivation of each crop based on HP filtering method is basically consistent with the development characteristics of agriculture economy in this region from 1991 to 2013,and it is consistent with time sequence development characteristics of different crops,which is a scientific and effective separation method.The unit climatic water deprivation of rape,grape,cotton,flax and apple crop in the Shiyang River Basin is more fluctuating,and the unit climatic water deprivation of all crops are becoming stable.The unit climate water deprivation of rape?grape?flax?apple and cotton crop in the Heihe River Basin is fluctuating with time.In addition to spring wheat and melon crop,the unit climate water deprivation of the rest of the crop are gradually stabilized.The volatility of climatic water deprivation of flax,grape,cotton,apple and potato crops in the Shule River Basin are higher,and the climatic water deprivation of potato,cotton,flax,rape,vegetable and apple crop are becoming more stable.(2)The results on the climate response of crop water deprivation based on the stepwise regression analysis show that not only the climatic influence factors of different crops are quite different,but also the difference of climatic driving factors of the same crop is still obvious,and the regional difference of response mechanism of water deprivation is significant.The climatic influencing factors of crop unit climatic water deprivation in Shiyang River Basin are concentrated at the average maximum temperature in July,and it is expressed to be positive driven.The main inhibitory factors of the climate water deprivation in the Heihe River Basin is the precipitation from May to July,and the driving factor is the wind speed from July to August.The main impact factors of crop's unit climate water deprivation in the Shule River Basin are the wind speed from May to June and the precipitation in July.The changes of crop water deprivation in the Shiyang River Basin are sensitive to the change of the temperature.Under the background of global warming,the climatic water deprivation of the crops will increase,which will be not conducive to the water-saving irrigation in the region.The Heihe and Shule River Watersheds are precipitation sensitive areas,however,the response mechanism of crop water deprivation to the trend of global warming is unclear.2.In terms of economic and technical driving factors of crop water demand(water deprivation and gray water demand)based on the method of LMDI.(1)Whether you analyze the total water deprivation(total gray demand)level of the watershed scale,or the type of crop,the effects of agricultural economic development and water deprivation intensity(gray water intensity effect)and their cumulative effects were the main incremental effect and reduction effect of water deprivation(gray water demand)respectively.Temporal variation characteristics and cumulative variation are of great difference among different crops in different watersheds.(2)Differences in different watershes of the decomposition effects of the total water deprivation and total gray demand changes.The agricultural economic effect is the main incremental effect of total water deprivation and total gray water's change in Hexi area and its valleys.Its influence direction remains stable and its upward trend is found in all valleys.The influence direction of population on two kinds of water demand is unstable,and population is the least contribution on two kinds of water demanded.The intensity effects of water deprivation and gray water demand are the most contributions on the influence direction,thereinto,the intensity effect of two kinds of water demand in Shiyang River Basin different has obvious different stages of change.The effect of crop structure adjustment on the two kinds of water's quantity demanded shows the inhibitory effect,this type of effect is second only to the water intensity.The influence direction of industrial structure on two kinds of water demand is unstable,thereinto,the industrial structure's accumulative effect of two kinds of water demand in Shule River Basin gets inhibitory effect while in other basins shows the promote effect.(3)Differences in different crops of the decomposition effects of the water deprivation changes:The agricultural economic effects of corn,potato,cotton,vegetables and grape in the Shiyang River Basin show an upward trend.The trend and waviness of the population effect of 10 crops are similar.In addition to spring wheat,the population cumulative effects of other crop are depressor effect.Industry structure adjustment cumulative effects of 10 kinds of crops are promote effect and the trend of flax crops is decreased.The planting structural effects have significant difference among different crops.Planting structure adjustment cumulative effect of spring wheat,rape and flax crop are inhibitory effect.Planting structure adjustment effect of flax and grape have an upward trend,while canola is opposite.The agricultural economic effects of potato crops,vegetable crops and grape crops in the Heihe River Basin have an upward trend,and the remaining crops have no trend.The effect of water deprivation intensity of spring wheat and rape crops have an upward trend and grapes and vegetable crops are opposite.Planting structure adjustment cumulative effect of the main crops are the inhibitory effect except for the grape crop,in which the planting structure adjustment effect of spring wheat and cotton crop have a downward trend,as well as the grape crop has a downward trend.The population cumulative effect of the main crop are the inhibitory effect and all crops have no trends.In addition to cotton crops,the industry structure cumulative effects of the rest of the crops are the promote effect and all crops have no trends.There is a clear upward trend in the agricultural economic effects of grape crops in the Shule River Basin,and there is no trend in the remaining crops.The effect of water deprivation intensity of the spring wheat and maize crops have an upward trend,but the melon crop has a downward trend.The planting structure adjustment cumulative effect of the vegetable,melon,grape crops are inhibitory effect.There is a downward trend of the structure adjustment effect of the potatoes and cottons.However,there is an upward trend of planting structure adjustment effect of melon and grape crops.The population cumulative effect and industrial structure cumulative effect of crops show a promote effect,but they all have no trends.(4)Differences in different crops of the decomposition effects of the demand for gray water:The differences of the demand for gray water exist among crops.The population effect of the change of the demand for gray water in the spring wheat,potato,oil,melon and apple crops in the Shiyang River Basin show an upward trend during the study period,and the other crops have no trends.The agricultural economic effects of corn,potato,cotton,flax,vegetable and grape crop all have upward trends,and the remaining crops show no trends.The planting structure adjustment effect of flax and grape crop planting show an upward trend,and the oil crop shows a downward trend,with the accumulation of the planting structure adjustment effect of spring wheat and rapeseed crops as incremental effects.The trend of all crops'industrial structure adjustment effect are not obvious,but the cumulative effect are incremental effect.The intensity effect of grey water in cotton crop shows a downward trend,and there shows an upward trend of flax,vegetables,apples and grape crops.The cumulative total effects are inhibition effect of the spring wheat,rape crops and the total effect of gray water in spring wheat,rape and apple crop show downward trend,and maize,flax,grape crop show upward trend.There is no trend of the population effects of all the crops'gray water demand in Heihe river basin,and the cumulative effect are all inhibitory effect.The agricultural economic effect of corn,potato,cotton,vegetable and grape crop show upward trends,and the rest of the crops have no tends.Planting structure adjustment effect of the grape has an upward trend,and the rest of the crops have no trends.Among them,spring wheat,maize,flax,rape and melon's planting structure adjustment effect are accumulated as inhibitory effects.The effect of gray water intensity of spring wheat crop shows an upward trend,and the vegetables and grape crops show a downward trend.In addition to the cotton crop,the accumulation effect of the industrial structure of the other crops are incremental effect.The total effect of the main crops'demands for gray water vary greatly.The total effect of the demands for gray water of the cotton and apple crops show a downward trend.However,the total effects of the demands for gray water of wheat,corn and potato crops show upward trend.The population effect of the main crops in the Shule River Basin show an upward trend,and the cumulative effects are incremental effect.The agricultural economic effect of potato,cotton,vegetable,gourd and grape crop show an upward trend,and there is no trend for the surplus crops.The planting structure adjustment effect of different crops are the reduction effect,and the planting structure adjustment effect of potato and cotton crop structure show an upward trend,and the melons and grape crops show an downward trend.The gray water intensity effect of melons and grape crops show a downward trend,and wheat and maize crops show an upward trend.The industrial structure adjustment effect of potato,vegetable,melon and grape crop show an upward trend,and the other crops have no trend.The effects of the total effect of the main crops are fluctuating,but the total effect of spring wheat,maize,flax,apple crop in most years show inhibition effect.The total effect of spring wheat,corn,vegetables,melons,grape crops show an upward trend,the remaining crops have no trend.3.In terms of optimizing allocation of water resources based on water footprint subdivision.By compressing the area of food crops,the method of virtual water trade is used to meet food demand.In both scenarios,Hexi area saves 2.38×10~8m~3 and 4.8×10~8m~3water resources,respectively.Virtual water trade is an effective way to solve the problem of regional water shortage and improve the efficiency of water use.By importing food crops and increasing the area of economic crop cultivation can increase the overall benefits of water resources.Because the economic crops,especially fruit crops,the demand for gray water is relatively large,so excessive increase such crop area is not ideal in the ecological benefits.It is necessary to further improve the utilization rate of chemical crops.Crop structure adjustment should be carried out on the premise of maintaining the total planting area,Hexi region should continue to compress the grain planting area,at the same time,improve the planting area of the vegetable,oil plants,cotton and potato crops.Especially,the planting area of vegetable crops should be greatly increased.After the optimization,the differences of the crop types between the basin increase and the interregional trade will be more frequent.